Experience from engine rebuild

[Tomas_Norway]

Thanks to the listers for answering my earlier questions.

I would like to share the experience I have made during my engine rebuild and upgrade. The car is a BN-7, and the engine used to be original.

The new specifications are:
- 84.5 mm Cosworth pistons (AH Spares)
- Balanced crank
- 2 x 2” HD-8 carbs
- Aluminium cylinder head, ported as the Works competition head (Webcon)
- 10:1 compression ratio
- Inlet manifold from Rawles Motorsport
- Tubular headers and big bore side exit exhaust (Dennis Welch)
- 278 deg camshaft (Dennis Welch)
- 1-2-3 electronic ignition
- Upgraded harmonic balancer (Dennis Welch)
- Lightened flywheel for upgraded clutch (Dennis Welch)

The crank must be balanced as the Cosworth pistons are much lighter than the originals.

The carbs are easy to tune, and the engine runs well even at small throttle openings.

Rawles inlet manifold: Good finish, and “looks” to be better than the original. Rawles claimed a 5% increase in torque. However, the customer support was non-existent after the purchase was made, even after several e-mails and calls. Not good. The throttle linkage worked well after some modification and head scratching. The choke arrangement was modified, but that would have had to be done anyway when changing from 1-3/4” to 2” carbs. The clearance to the bonnet is too small, and I got a small dent in the bonnet above the front carb after the first drive... In retrospect I am not sure this manifold is worth the extra trouble and expense. Porting the original manifold may be a simpler and cheaper solution, with only marginally less power.

The crankcase ventilation must have a PCV valve to avoid a lot of vacuum in the engine. I found one from an old Dodge which fitted onto the hose. In my ignorance I did not fit one at first and fouled the plugs with oil after just a few miles.

I have not had the engine dyno checked yet, but it is definitely a LOT more powerful than it used to be, and can easily out-accelerate an original BJ-8. What is even more pleasing is the very good torque from as low as 1100 rpm, with plenty from 1500 rpm. The behaviour at low revs is much better than what I expected. The real power kicks in at 3000 rpm and the engine is happy to rev to 5500 – 6000, accompanied by a very nice and racy exhaust note... The idle is slightly rougher than it used to be, I have set idle to 950 rpm.

I do not claim to be a “guru” of engine tuning; this is just my experiences and opinions...

What is missing is a rev limiter, but I am not sure what would work well with my ignition.

 

[HealeyPassion]

Thomas,
Sounds like a nice package! You should have a lot of fun with that before the snow arrives!

Cheers,
Steve
Larkspur, CO
https://stevesaustinhealey.com

 

[glemon]

"what is missing is a rev limiter"

Isn't it fun to have a motor you feel you need one on????

Sounds like an excellent rebuild I know of some guys who have gone to far with performance moda and gotten a car that is not fun to drive on the street, sounds like your emphasis on torque and some more high end has gotten you a well balanced package.

 

[Patrick67BJ8]

Thanks to the listers for answering my earlier questions.

I would like to share the experience I have made during my engine rebuild and upgrade. The car is a BN-7, and the engine used to be original.

The new specifications are:
- 84.5 mm Cosworth pistons (AH Spares)
- Balanced crank
- 2 x 2” HD-8 carbs
- Aluminium cylinder head, ported as the Works competition head (Webcon)
- 10:1 compression ratio
- Inlet manifold from Rawles Motorsport
- Tubular headers and big bore side exit exhaust (Dennis Welch)
- 278 deg camshaft (Dennis Welch)
- 1-2-3 electronic ignition
- Upgraded harmonic balancer (Dennis Welch)
- Lightened flywheel for upgraded clutch (Dennis Welch)

The crank must be balanced as the Cosworth pistons are much lighter than the originals.

The carbs are easy to tune, and the engine runs well even at small throttle openings.

Rawles inlet manifold: Good finish, and “looks” to be better than the original. Rawles claimed a 5% increase in torque. However, the customer support was non-existent after the purchase was made, even after several e-mails and calls. Not good. The throttle linkage worked well after some modification and head scratching. The choke arrangement was modified, but that would have had to be done anyway when changing from 1-3/4” to 2” carbs. The clearance to the bonnet is too small, and I got a small dent in the bonnet above the front carb after the first drive... In retrospect I am not sure this manifold is worth the extra trouble and expense. Porting the original manifold may be a simpler and cheaper solution, with only marginally less power.

The crankcase ventilation must have a PCV valve to avoid a lot of vacuum in the engine. I found one from an old Dodge which fitted onto the hose. In my ignorance I did not fit one at first and fouled the plugs with oil after just a few miles.

I have not had the engine dyno checked yet, but it is definitely a LOT more powerful than it used to be, and can easily out-accelerate an original BJ-8. What is even more pleasing is the very good torque from as low as 1100 rpm, with plenty from 1500 rpm. The behaviour at low revs is much better than what I expected. The real power kicks in at 3000 rpm and the engine is happy to rev to 5500 – 6000, accompanied by a very nice and racy exhaust note... The idle is slightly rougher than it used to be, I have set idle to 950 rpm.

I do not claim to be a “guru” of engine tuning; this is just my experiences and opinions...

What is missing is a rev limiter, but I am not sure what would work well with my ignition.

The Rawles manifold looks like the one from DMD in Ox. Why did you choose that one?
I was told of a "Derrington" grind camshaft that was better than the original BJ8 camshaft off the line but I haven't found anyone who has one. Not to find any fault with what you've done...maybe a little envious!! LOL
Patrick

 

[hama61]

Hello Tomas,

I have sent you a pm

Harry

 

[Tomas_Norway]

Patrick,

I did not know of the DMD manifold until now. After looking at the DMD website, I can tell that the DMD manifold is not the same as the Rawles manifold.

Tomas

 

[Patrick67BJ8]

Patrick,

I did not know of the DMD manifold until now. After looking at the DMD website, I can tell that the DMD manifold is not the same as the Rawles manifold.

Tomas

Maybe different Customer Service too??
Patrick